Yes, it is possible to install an aftermarket exhaust on a KTM Duke 200 BS6 while retaining the catalytic converter. Many aftermarket exhaust systems are designed to be compatible with the stock catalytic converter, allowing you to enhance the sound and potentially improve performance without compromising emissions compliance.
By altering the exhaust flow characteristics, you may experience slight changes in the air-to-fuel ratio and engine tuning, which could affect the overall efficiency of the motorcycle.
The extent of the impact on mileage will depend on various factors such as the specific aftermarket exhaust system, your riding style, and the overall condition of your motorcycle. In some cases, the difference may be negligible, while in others, you may notice a slight decrease in fuel efficiency.
If mileage is a significant concern for you, it's advisable to research and choose an aftermarket exhaust system that is specifically designed to balance performance enhancements with minimal impact on fuel economy. Additionally, ensuring proper installation and maintenance of the exhaust system can also help optimize performance and efficiency.